Inside the Factory

Gregg Wallace is in Stoke-on-Trent at an enormous cherry bakewell factory where they produce 250,000 little tarts every day. He follows the production of cherry bakewells, from the arrival of 27 tonnes of flour right through to dispatch. Along the way, he learns what makes a shortcrust pastry ‘short' and discovers the simple way they ensure every cherry is precisely placed. They employ a team of 12 who carefully pop each one on top by hand.

Meanwhile, Cherry Healey is learning how to swerve a soggy pastry bottom when baking pies and tarts at home. She discovers that it is all about a pre-heated oven, a proper pie dish, rolling the pastry to the correct thickness and blind baking. And she is at an almond butter factory, learning how almonds are roasted and milled to become a thick spread ready for toast.

Historian Ruth Goodman is sniffing out the origins of one of the cherry bakewell's key ingredients, frangipane. She learns that, surprisingly, the familiar fragrant almond filling was born out of a perfume used to disguise the foul smells of 17th-century Paris. She also visits the Peak District town of Bakewell and learns how the modern cherry bakewell is a descendent of a simple recipe mistake in the kitchen.

Gregg Wallace is in South Shields at a clothing factory where they produce 650 waxed jackets a day. He follows the production of water-resistant jackets from the arrival of 500-metre-long rolls of undyed cotton through to dispatch. Along the way, he sees the fabric dipped into baths of wax heated to 95 degrees Celsius and learns how a 23-piece pattern is used to create a complex 3D jacket jigsaw.

Meanwhile, Cherry Healey is learning about the science of staying dry. She finds that it is easy enough to waterproof a fabric by coating it in a non-permeable coating. But while this stops water getting in, it also stops sweat getting out. The key to comfortable rain resistance is a breathable membrane which contains microscopic holes, big enough to allow steam to escape, but too small to let rain drops in. Cherry also visits an umbrella factory, where manufacturing methods have barely changed in 150 years. She helps transform a simple wooden stick into a top-notch canopy using saws, pliers and needle and thread.

Historian Ruth Goodman is investigating the fishy origin of waxed jackets. She visits a remote Scottish harbour and learns how these weatherproof coats were born out of oil covered sail cloth which seamen adapted into garments to keep out the worst of the weather. She also visits Edinburgh and learns how an English King played a key role in the popularity of that favourite Scottish fabric, tartan.

Gregg Wallace is in France at an enormous croissant factory where they produce 336,000 of the flaky pastries every day. He follows the production of croissants from the arrival of 21 tonnes of butter right through to dispatch. Along the way he learns how they use an 83-year-old strain of yeast to pack a flavourful punch and discovers the secret of pastry lamination. They layer very thin slices of butter between sheets of dough to create the famous flaky pastry.

Meanwhile, Cherry Healey is testing the best way to eat a croissant. With the help of a professor who specialises in the science of our senses, she discovers that there is an optimum way to consume them. Ideally, they will be served warm so that the butter inside oozes fat into the pastry, smothered in jam to give a sugar and fat hit, and eaten from a paper bag so that the crinkly sound accentuates the flaky texture of the pastry. She also heads to north Wales, visiting a farm and dairy where they produce a special type of ‘concentrated' butter. The butter is a whopping 99.8% fat, perfect for producing croissants with a long shelf life.

Historian Ruth Goodman is in Paris investigating the croissant's surprising Austrian origins. It is thought that it originated with a pastry called a kipferl, which Austrian bakers invented in the 17th century to commemorate a heroic victory over the armies of the Ottoman Empire. Its shape was a mocking reference to the crescent on their enemy's flag. But it took a while to transform into the modern pastry - the earliest written recipe she manages to find for a modern French croissant comes as late as 1906. Ruth also discovers that bread played a vital role in the French Revolution.

Gregg Wallace is in Leeds, at an enormous mattress factory where they produce 600 bouncy beds every day. He follows the production of pocket-sprung mattresses from the arrival of hard steel right through to soft bedding heading out of dispatch. Along the way he learns how lengths of metal are stretched into thin wire and coiled into springs which are placed into individual pockets. And how the mattresses are designed to wick sweat away from our bodies with the help of natural fibres like hemp and wool.

Meanwhile, Cherry Healey is learning whether there are benefits to be had from taking an afternoon nap. She meets up with a sleep scientist who tells her that we should be making time for a snooze rather than reaching for a cup of coffee. To prove his point, he runs an experiment which demonstrates that reaction times can be improved by a short sleep. 20 minutes is the optimum nap time - any longer risks falling in to a deep sleep which is difficult to wake from. And she is visiting a sheep farm where she sees how wool is shorn and discovers its amazing anti-bacterial and fire-retardant properties, which make it perfect for lining a mattress.

Historian Ruth Goodman is investigating the origins of the modern mattress. She lies down on a straw stuffed sack which the lower classes would have slept on in the middle ages and learns how steel transformed our bedtime habits, first with the 'innerspring' and then with the more comfortable 'pocket spring' technology. And she learns how a famous Scandinavian inspired home store is responsible for our enduring love affair with the duvet.

Gregg Wallace is in Cornwall at an enormous bakery where they produce 180,000 Cornish pasties a day. He follows the production of the pastry snacks from the arrival of two tonnes of swedes right through to dispatch. Gregg learns that there are very specific rules to creating a Cornish pasty. They must be made in Cornwall, the filling can only contain onion, potato, swede, beef and some seasoning - and each ingredient must be cooked from raw within the pastry parcel.

Meanwhile, Cherry Healey is delving into the wonderful world of the onion. She peels back the layers to discover the science that makes it such a versatile vegetable, and more importantly, why it makes us cry. It is all down to a chemical called lachrymatory factor, which is only created when an onion is cut into. Cherry visits an anaerobic digestion plant, where they turn waste from food factories into electricity. Micro-organisms feed on food waste, producing methane gas, which is used to power generators.

Historian Ruth Goodman is debunking some common Cornish pasty myths. It has been claimed that the county's tin miners invented the pasty as a convenient snack to eat while they toiled at the rock face. She learns that miners may have eaten them, but they didn't invent them. And it is unlikely that they used the pastry crimp as a handle. She also visits the Worshipful Company of Grocers in London, which was responsible for importing pepper into Britain. She learns how this ubiquitous seasoning transformed from a commodity so valuable it was known as black gold to a spice that everyone could afford.

Gregg Wallace is in France at an enormous foundry that produces a cast iron pot every five seconds. He follows production of casserole dishes from the arrival of 20 tonnes of crude iron right through to brightly coloured orange pots. Along the way, Gregg tests his mettle by taking a sample of molten iron at 1,550 degrees Celsius. With only a heatproof visor and gloves as protection, he dips a ladle into a bubbling cauldron and pours the white-hot sample into a tiny mould. He also discovers that the coloured enamel they protect their pots with is made from glass.

Meanwhile, Cherry Healey is in South Africa visiting one of the largest iron ore mines in the world. Nine miles long by three miles wide, it produces a staggering 670,000 tonnes every day. Cherry rides in one of the biggest dumper trucks in the world. Seven metres tall and packing 2,500 horsepower, it collects 65 tonnes of freshly mined rock and dumps it in to a processing plant. Days later, the iron ore is taken away from the mine in a two-mile-long train. And Cherry is rooting out the science behind cooking the perfect casserole. It turns out that when it comes to cooking time, longer isn't always better.

Historian Ruth Goodman takes a journey through time, learning how one-pot cooking evolved. From communal ovens during the industrial revolution through to 1970s slow cookers, technology influenced how people prepared simple meals. Ruth also visits the birthplace of the industrial revolution in Shropshire to discover how casting iron in sand moulds democratised our kitchens by producing affordable cookware.

In Wigan, Gregg Wallace visits an enormous soup factory, which produces two million tins a day. He follows the production of vegetable soup, from a pea harvest in Yorkshire right through to the finished soup going into cans and being dispatched. Along the way, Gregg watches as a five-tonne avalanche of peas – around a million individual peas – is frozen within two hours of being picked. He mixes up three tonnes of veg and 500 gallons of tomato sauce and watches as they are combined and packed into 10,000 tins. Gregg is astonished by a 27.4m-tall pressure-cooking tower and surprised to learn that for every one degree drop in temperature in winter, the factory observes a 3.5% increase in soup sales.

Meanwhile, Cherry Healey is measuring the vitamin content of fresh and frozen vegetables. She finds that her sample of frozen peas have six times the vitamin C content of fresh, while sprouts do even better with 800% more. Cherry travels to a rock salt mine outside Crewe, which supplies half of all salt used in the UK food industry, and runs an experiment to see if soup could be the answer to staying fuller for longer.

Historian Ruth Goodman is cooking up a batch of ‘soop of buttered spinach' from the 17th-century cookbook of Robert May. This is the first reference to a recipe for soup in English, but the resulting sweet, vegetable puree doesn't resemble soup as we know it today. She also heads to Poplar in east London to a Salvation Army soup kitchen. Here, Ruth discovers that the notion of the soup kitchen originally began in 1795 as a response to a countrywide harvest failure.

Gregg Wallace is in Ireland at an enormous liqueurs factory that produces 540,000 bottles a day. He follows the production of cream liqueur from the arrival of maize to make Irish whiskey right through to dispatch of the finished liqueur. It is the show's longest ever production timeline, taking more than three years. Along the way, Gregg learns that it is the barrels whiskey is matured in that create around half of its flavour and discovers that a milk protein is the secret to mixing cream and whiskey together.

Meanwhile, Cherry Healey is at the plant where 85 per cent of Ireland's bottles and jars are recycled. They process 500 tonnes every day. Cherry also investigates the science behind aperitifs. There is nothing special in these beverages that stimulates appetite - it is something common to all alcoholic drinks. Cherry puts it to the test with a team of rugby players and discovers they eat 8 per cent more – or an additional 320 calories – when alcohol is involved. Cherry is also getting a lesson in the rules of whiskey, learning that single malt must be made from 100 per cent malted barley from a single distillery, whereas bourbon must be 51 per cent maize, and blends can be the product of a mix of grains from different distilleries. The one thing they have in common is that they must be matured in wooden barrels for a minimum of three years in order to be called whiskey.

Historian Ruth Goodman is getting spiritual with the history of liqueurs. She learns that their origins are to be found a world away from funky downtown bars. She visits a former monastery and discovers that the drinks were invented by monks looking for the elixir of life. Ruth also visits a distillery in Ireland, where she learns that 100 years ago Irish whiskey held an astonishing 60 per cent of the global whisky market. Today, it is just 5 per cent. This drop was largely due to resistance to adopting the modern column still method of distillation.

Gregg Wallace is in Essex at an enormous cereal bar factory, which produces 400,000 fruit- and nut-packed treats a day. Gregg follows production from the arrival of two tonnes of macadamia nuts all the way through to dispatch. Along the way, he gets hands on with all the ingredients, from nuts to cranberries and sultanas to puffed rice. He learns that it takes a carefully balanced blend of honey and glucose to bind the ingredients together. Too much honey and the bar would be too chewy. Too much glucose and it would set rock solid. A mix of both produces the ideal texture.

Meanwhile, Cherry Healey is helping out with the macadamia harvest in South Africa. The country is the world's largest producer of these nuts, responsible for a quarter of the global harvest. She learns that the trees they grow on can take seven years before they produce their first crop, partly explaining why these nuts are so costly. She also discovers that their super tough shells require pressure equivalent to being sat on by a baby elephant to break them open. In the UK, Cherry visits the Eden Project in Cornwall and learns that nuts aren't all they seem - only a small percentage of what we commonly refer to as nuts are actually botanical nuts. Peanuts are legumes and cashews are drupes. However, everything we refer to as a nut is the reproductive part of the plant and packed full of nutritional goodness.

Historian Ruth Goodman climbs a mountain in the Lake District to meet an explorer who tells her all about one of Britain's original snack bars, Kendal Mint Cake. Its popularity grew after famous explorers Ernest Shackleton and Sir Edmund Hillary took it on their expeditions to Antarctica and Everest respectively. Ruth also visits the home of Britain's very first cereal bar to learn how it went from simple hippy food to shifting three million bars a week.